1. Field of the Invention
The invention relates to a low power apparatus for detecting the validity and denomination of a coin.
2. Description of the Prior Art
There is believed to be a substantial need for low power coin discriminators for use in devices such as parking meters, telephones, and vending machines. Most prior art coin discriminating apparatuses tend to be mechanical in nature. Only a few moderately reliable electronic devices are known. Since most prior art electronic devices are located near a source of power, the problem of power consumption has never been a major concern. However, there are certain environments, such as parking lots, where external power isn't available. Therefore, it was necessary to search for a low power, highly accurate and highly rugged unit. Since no prior art devices appeared to fit that description it was necessary to invent one that did.
The use of piezoelectric elements in the context of coin discrimination is not common. However, U.S. Pat. No. 3,776,338 does disclose a piezoelectric detector used for detecting the presence of a coin. The use of a rudimentary striking pad to cover the surface of a piezoelectric element is also discussed. Another discussion of the use of piezoelectric elements is found in an article entitled "Poly(vinylidene) Fluoride Used for Piezo Electric Coin Sensors". The article was written by G. R. Crane of Bell Labs and appeared in Volume SU 25, No. 6, (November 1978) of the IEEE Transactions on Sonics and Ultrasonics at pages 393-395.
Some prior art references describe systems which employ two or more steps to detect coins. For example, U.S. Pat. No. 4,082,099 discloses a two step method for coin discrimination. The first step is the detection of the coin by a metal sensor. The second step employs photoelectric elements. Similarly, U.S. Pat. No. 4,436,196 discloses another two-part test and includes a discussion of the use of an LED and a microprocessor. Likewise, U.S. Pat. No. 3,211,267 discloses a dual test to determine the weight and diameter of the coin.
A number of prior art references discuss the use of other photoelectric devices to detect the presence and/or areas and/or diameters of coins. Note specifically that U.S. Pat. Nos. 3,978,962; 4,249,648; 4,267,916 and 4,474,281 disclose the use of arrays of LED's to detect coin parameters such as velocity, area, diameter, etc. Other patents of interest with regard to the photoelectric detection aspects of the present invention are U.S. Pat. Nos. 3,939,954; 4,436,103 and 4,442,850. Insofar as understood none of the prior art references cited above or known to the inventor have the same structure or function as the unique invention described herein.